The city of Arcata has received its first payment from Pacific Gas and Electric Co. for its excessive electricity users tax, but officials say it is too early to project if the tax will bring in the anticipated $1 million in revenue.

”We need about four or five months before we can note any trends,” Environmental Services Director Mark Andre said. “It’s just one snapshot.”

The $50,000 payment from PG&E for October and November will be put in the city’s general fund. It cost the city $650,000 to implement the tax.

Measure I, the so-called marijuana grow tax, assesses a 45 percent tax on households that use more than 600 percent of the energy baseline — or the energy used to power three average homes. It was passed by voters in November 2012 with the hope of reducing the city’s greenhouse gas emissions after they rose by 30 percent from 2000 to 2006.

”I’m very pleased with how effective this has been,” Councilman Michael Winkler said. “I feel that the new tax has been extremely effective in reducing the number of residences that are exceeding the threshold.”

In the first month, 96 PG&E accounts were over the baseline, according to Andre. Of the 9,500 residential meters in Arcata, 633 previously exceeded the 600 percent mark.

”I think it’s safe to say all the reduction is in large-scale marijuana grow houses,” Winkler said. “This is the goal that we as a city have been trying to achieve with this tax. We achieved it a lot faster than I expected.”

Councilwoman Alex Stillman said the city will have a better idea of the tax’s effectiveness in six months.

”We need to have at least six months of information before we can make any type of determination — if it’s working or not working,” Stillman said. “It’s way too soon, in my opinion, to make a determination.”

As Arcata waits for more data, the Humboldt County Board of Supervisors and Eureka City Council are considering moving forward with a similar tax after concerns arose that growers would move out of Arcata into other jurisdictions.

The board of supervisors voted unanimously last month to have PG&E provide it with data related to potential high energy use in unincorporated areas, while the Eureka council unanimously voted to have PG&E survey the city’s meters to determine how many customers are above the 600 percent threshold.

Arcata will receive its next installment at the end of this month, PG&E spokeswoman Jana Morris said.